摘要： # GCD&LCM&Eluer——推柿子 ## 一、$\sum_{i = 1}^{n}[\gcd(i,n)=d]$ $\sum_{i = 1}^{n}[\gcd(i,n)=d]$ $=\sum_{i = 1}^{\frac{n}{d}}[\gcd(i,\frac{n}{d})=1]$ $=\phi( 阅读全文

摘要： # [UNIQUE VISION Programming Contest 2023 New Year (AtCoder Beginner Contest 287)](https://atcoder.jp/contests/abc287) ## A - Majority ### Problem Sta 阅读全文

摘要： # [AtCoder Beginner Contest 278](https://atcoder.jp/contests/abc278) ## A - Shift ### Problem Statement 题意：给你一个长度为n的序列，让你移走前面k个后面补k个0。 ### Solution 思路 阅读全文

摘要： # [AtCoder Beginner Contest 284](https://atcoder.jp/contests/abc284/tasks) ## A - Sequence of Strings ### Problem Statement 题意：给你n个字符串，让你倒序输出 ### Solu 阅读全文